Evidence from prior spills, such as the Exxon Valdez suggests further long-term effects. "Salmon embryos exposed to oil, when they grow up, their babies are compromised, through mechanisms such as messing with the [hormonal] system," says biologist Andrew Whitehead of Louisiana State University, who studied Louisiana marshes both before and after the oil spill. Alaskan shorebirds also did not breed as much, had smaller eggs when they did breed, and those chicks that did hatch died more frequently.
In addition, BP's Macondo well oil itself smothered birds; more than 8,000 such birds representing 102 different species were collected—2,263 of them already dead—by government workers. Of course, this is likely just a fraction of the birds impacted because an oil-coated bird at sea sinks. "It is this phenomenon that makes an accurate estimate of bird deaths extremely difficult," wrote the Congressional Research Service in an October report on oil spill ecosystem impacts. The Center for Biological Diversity estimates that the oil spill killed or harmed approximately 82,000 birds as well as more than 6,000 sea turtles and 25,000 marine mammals, such as various species of dolphins.
And, unfortunately, the oil that did reach the coast—nearly 700 kilometers of marshland and 235 kilometers of beach was oiled, according to the government's Shoreline Cleanup Assessment Teams—"is very persistent once it gets up in the marsh grass," Miles says. "We still have a lot of oil in the Louisiana marshlands." That oil killed the spartina marsh grass at times, reducing coastal wetlands and, ultimately, exacerbating coastal erosion. "If it does kill the grass in high enough concentrations and a big storm comes up, it's going to start eroding," Miles adds.
At the same time, the closure of Gulf fisheries during the oil spill last year removed the enormous pressure from commercial fishing on populations ranging from shrimp to the tiny fish known as menhaden, the latter of which is caught to be ground up into meal. As a result, fishing this year is some of the best ever. "There are some fish species that are not as prolific as they have been. Others, there are millions, because we didn't fish them last year," Mobile Bay's Callaway says. "The food web has been touched and changed. We just don't know what that means."
And the fact that the spill occurred at sea—and beneath 1,500 meters of water—spared some of the most productive fisheries and spawning grounds in the world. "What is arriving at shore is much less toxic, much less difficult to deal with than what is coming out of the wellhead," says biologist Christopher D'Elia, dean of the School of the Coast and Environment at Louisiana State University. "If [the spill] had been closer, we would have been in much more trouble."
In the meantime, the Gulf shores enjoy a profusion of tarballs and tar mats in excess of the ones that are always present as a result of natural seeps. "I have spent every summer of my life in Gulf Shores, [Ala.,] and I have never seen anything that is remotely close to what we have here now," Callaway says. "You just run your fingers through the sand and you've got hundreds, depending on when the last time they did a deep clean."
Such "deep cleans" have their own impacts. "There weren't sand crab holes anywhere—those are a major chunk of the food web," Callaway adds. "I didn't see periwinkles or clams along the shoreline. I'm hoping that is temporary and not long-lasting."
But evidence from prior oil spills suggests that Macondo well oil will be a part of the Gulf Coast for a very long time. "Oil persisted for much longer in the environment than anyone expected," Whitehead notes of the Exxon Valdez spill. "The oil was gone from the surface pretty quickly but sediment-associated organisms were persistently exposed to oil over long periods of time—we're talking five to 10 years after the spill."